Method os treating- moldings of partially-cured phenolic condensation



May 3.1927., 1,627,209

F. SMITH METHOD 0F TRATING HOLDINGS 0F PARTIALLY CURED PHENOLIC CONDENSATION PRODUCT I ATTORNEY y F. s. SMITH IIETHOD 0F TREATING MOLDINGS OF PARTIALLY CURED PHENOLIC CONDENSATION PRODUCT Filed July 29, 1924 2 sheets-Sheet 2 12 I. IgENTER 16' "1 2 BY l ATTORNEY Patented May' fi,

N entre stares Pitti?.

QCGNR T0 IRODUCTS .PRO- lil. Y., A CGBJPRATON OF DELAWARE.

Application :filed July 9, 1924.

The general object ot' my invention is to provide both a novel method and a novel apparatus tor producing molded articles of phenolic condensation product suitable lor use for the various purposes tor which such product is adapted; lor example, high voltterminals ior electric transiormers such as are disclosed in my applications 'for Letters Patent, Sr. llos. lillLQ/l and hilllll). :tiled March 2nd, 192i, and March 17th7 1922, respectively.

In use such terminals are subjected to high internal gas pressure7 the said pressure being on the order ot l'il'teen atmospheres per square inch. lt is essential, therefore, that the tensile strength. and density ot the said 'terminals shall be as great as possible. Likeivise the dielectric strength also should be as high as possible and the external suri'ace .resistivity is oit especial .importance -for outdoor operation. 'lhe material usually employed for melding such terminals consists ci. Wood 'flour impregnated with phenolic condensation product. The 'trictional resistance ot such mixture to flow Within a mold is great even at the optimum molding temperature.

In practice all moldings oi these materials made .in mechanical molds are oi' heterogeneous density. Usually the larger the molding, that is the thicker the Walls, the less unitorm :is the density. Such nomini- 'tormity ot density is especially apparent in large articles or moldings-'lor instance articles or moldings ot the order ot ten (l0) pounds and oit the contigui-ation illustrated in the drawings et this application. By a mechanical mold is meant one in which the molding material is compressed and caused to lloiv by one or more plungers movable relatively to the chase of the mold.

in my application 'tor `lietters latent ol' he United States liled September 15th, i920, 'li'. No. lll 0,4156, .l have disclosed a method ol molding phenolic condensation product in which the mixture oi Wood tlour and phenolic condensation product is subjected to a prohosting and drying operation prior to 'the placing oit the saine in molds tor molding the same into the t'orm oi such articles as may be desired. lllhile the said method posmany adrant over the methods .ously known .s open to the obieotion Serial No. 728,985.

that the articles produced thereby are not ol uniform density ivhicln however, is due to the tact that the article is molded in a mechanical mold and the curing` process coinpleted with the article therein. @n accoum et the non-uniform density ot articles oi" phenolic condensation product which are molded Within a mechanical mold and cured therein the Wall thickness ot such articles, as tor example high voltage terminals, must conform to that thickness which is suitable or requisite ior the portion ot lowest density of the molding. ln the case oit' moldings tor use as high voltage terminals the characteristie oi non-uniformity present in moldings made according to previously known processes or methods necessitates a structure of considerably greater Wall thickness than would be necessary il the density oi the moldings were ol uniform density equal substantially to the maximum density throughout 'the structure.

Such lack ot uniformity in the density in the molded articles entails greater expense in the making ol the moldings than should be necessary. @ne item ot increased expense consists ot the increased amount of material which of necessity must be used to increase the Wall thickness so as to provide that at the point ot least density the requisite strength shall be assured. lil/'hen the molded article is cured in the mechanical mold by Which it may have been termed there is not only the expense incident to the tying up ot the mold dining the curing process but also the expense incident to the length of time required for the curing process. These two items combined constitute the greatest item et expense involved in the methods as hereto- 'fore practiced. 'lhe principal object ot my present invention, therefore, is to make better moldings, cheaper moldings and to iiicrease the external surface resistivity thereof.

in the carrying` out ot the method embodying the present invention the mixture ot Wood 'flour and phenolic condensation product, ilorm A, :is subjected 'tirst to a drying and preheating process as is described in my application Sr. No. i-107456, above referred to. rl`he mixture having been subjected to a drying and a prei" "iting treatment at a temperature belen' its tral'isition pointf a little below eighty degrees centigrade, it is then packed or rammed into a mechanical mold which is closed by means of an hydraulic press, and the material partially cured therein.l The Vperiod of such partial curing depends primarily upon the wall thickness of the molding. A molding having a wall an inch in thickness should be kept in the mold for partial curing` around ten minutes. The curing should be effected from the inside of the mold outwardly. rThis may be accomplished by providing that the mandrel within and upon which 'the molding is formed may be heated to a higher temperature than the external portion or chase of the mold. After the mixture has `been placed in the mold, as above described, the temperature is raised to a temperature sufiicient to transform product A to product C, say on the order of 14:00 C.

` After the moldinghas been partially cured in the mold in which it is formed it is removed with the mandrel and quickly (to avoid teinperature drop) placed within a liquid which preferably should be chemically neutral with respect to the material of which the molding is composed and 4of greater Viscosity than water. lt is desirable that the liquid used should be relatively viscous as otherwise it would tend to seep in between the mandrel and the .product under treatment as will be apparent in the following.

` It is essential that this material should be liquid at the ltemqperature of treatment and asolid at normal atmospheric temperatures at which `the finished product is to be used. Such liquid preferably consists of cuman a dielectric, which lis a synthetic resin produced from coal tar distillates. Chemically it is a mixture of para-corunarone, para-indeue and the polymers of other hydrocarbons found in. coal tar. At normal atmosplleric temperature cumar is a solid but at thetempera ture at which the curing is effected, one hundred and forty (140) degrees centigrade or higher, the said substance is a liquid of sutlicient viscosity. Instead of cumar7 chlorinated napthalene (known in the trade as halowax) also a dielectric may be employed. f

liv/Whether the one or the other of these substances `is employed the` said substance is placed in a receptacle of the static press and when melted the molding with the mandrel upon which it is molded. and carried in its original relative position is inserted and supported within the receptacle of said static press, the said molding` being` submerged in the hotliquid. The said liquid is thenvery quickly subjected to a static pressure on the order of one ton per square inch. `The static pressure must be applied quickly otherwise the liquid will seep in between the mandrel and the product under treatment. By the use of this viscous liquid and by a quick application of the static pressure, the use Aof the rubber or other packing usual in hydrostatic pressing of materials is eliminated. The molding is left in this liquid under pressure and at a temperature of around one hundred and forty (140) degrees centigrade or higher until. the curing,` is effected. ,i

Although I have mentioned specifically cumar and chlorinated napthalene suitable materials to be employed for the formation of the liquid within which the molding is to `be submerged and cured, it should be understood that any other relatively viscous liquid suitable which is chemically neutral with respect to the material of the molding; may be employed.

The liquid employed, however, preferably should be one of such character that it will combine mechanicallyr with the external surface `of the molding and it should preferably be of such character that the surface resistivity of the molding will be increased by the incorporation of the outer portion of the molding with portions of the material within which the curing is effected. The extent to which the liquid within which the curing is eii'ccted may penetrate the molding` may be controlled by the extent of the curing of the said molding within the mechanical mold before subjecting the same to the action of the liquid under static pressure, as above described.

The mechanical bond which is veffected during the curing operation between y the molding material and the ccumar appears to be lasting. The resultant surface is speckled, that is, there are many small isolated speeks of cumai which add greatly to the surface resistivity and tend to prevent wetting` of the molded article when it is subjected to the weather. The `surface in that respect has somewhat the characteristic of a wax. l

A further advantage vincident to the use of cumar as the materialA in which the curing; is effected is that itis a completely polymerized' substance which is a desirable characteristic of the material employed in the curingprocess of a molded phenolic condensation product.

In the preceding,` portion of Vthis specification l have described the method en bodyingmy invention in a general way without referring` to mechanism but obviously some form of mechanism is necessary in practice to carry out the invention commercially and l have, therefore, provided an apparatus which may be employed in the carrying,` out of the method. The machine or apparatus employed by me is believed to be novel but it will be yunderstood that the method, as above described, and which embodies my invention is not limited to any partielular kind or form of mechanism but may be ried out by the use of any apparatus or ma icc It will be observed that the mandrel 4.10 isV provided with a shoulder intermediate its ends by which the upper end of the molding is formed and against which it is seated, as shown in the drawing. Adjacent 'the shoulder 65 the said mandrel is provided The Iparticular molding disclosed is intended for use in connection with high voltage terminal structures and the internal screw-threaded portions are provided for the purpose of making certain necessary attachments.

In the operation of the apparatus and in the carrying` out or practicing ot' the method the molding is irst molded upon the mandrel 40, or a similar mandrel ina mechanical mold and given a preliminary curing treatment therein, as above described. ln this preliminary curing operation the interior oi' the mold, that is to say, the mandrel should be at a higher temperature than the exterior mold member in order that the curing may proceed from theinterior toward the exterior of the molding.

'.lhe preliminary curing` having been completed the mandrel with the molding thereon ask shown in Fig. 2. is transferred to an apparatus such yas illiilstrated and is secured in place upon the stationary member' l2 with the outer upper terminals 68 of the extensions 58 of the resistance wire 52 in contact or engagement with the line wires which communicate with the source of electric current supply not shown. The exterior member 5 of the press having been previously supplied with a suitable material, such as cumar, is heated, the cumin liqueiied and maintained at the desired temperature. This material constitutes the liquid. 6. rlhe member 5 is then elevated by means of the plunger 1S so that the molding is submerged within the said liquid 6. By reason of the upwardmovement of the external member 5 of the' press the stationary piston like member 4t2 is caused to the upper thereof, as shown in Fig. 1 of the drawings, so that the liquid 6 within the member may be and is subjected to great pressure, the pressure being on the order of two thousand pounds per square inch. It may be noted here that the upward movement ofthe member 5 under the influence of the ram or piston 18 is adapted to be limited by the shoulder 0 near the upper end portion of the mem- The molding having been submerged within the liquid 6 is retained therein under the pressure indicated during the period that the curing is being effected which may be several hours, the length of timev depending upon the thickness of the molding. The curing should beeiiected at a temperature on the order ol 1st() degrees. As already indicated, during the preliminary curing vin the mechanical mold in and by which the molding is originally formed the `temperature of the interior should be greater than thatvof the exterior in order that the curing or change of form may take place from the interior towards the exterior of the molding. lVhen the curing is ei'l'ected in this manner the gases which may be present within the body of the materialof whichthe molding is composed are caused to escape outwardly through the molding while it is in a permeable condition. By this method the formation of porous or defective portions is prevented. Likewise during the curing operation within the apparatus disclosed and described herein the mandrel 40 should be maintained at a higher temperature lthan thatof the external member 5 of the press.

After the curing of the molding has been completed the ram or piston 18 is lowered so as to lower the external member of the mold structure. The mandrel 40 is then disengaged and removed lrom the stationary piston-like member 42 and while the mold- 'ing l1 is still hot it is turned so as to remove orback it oli" of the mandrel 40. The molding is then cooled very slowly to `room temperature.

It will be observed that in the carrying out of the method embodying my invention the interior of the molding is shaped by the mandrel from which it is not removed until the curing thereof has been completed so that the inner surface which in the molding as illustrated is the important surface is maintained in its original accurate shape and contour. f l

Having thus described my invention what l claim and desire to secure 'by Letters Patent is:

l. The method ot treating moldings of the said mold and placing it within a liquid 'dielectric ci" viscnsity than. water and Mig simultaneously subjecting the same to heatV Aand pressure, the pressure causing a portion oit said dielectric to penetrate said molding.

2. rl`he method ot treating moldings ot phenolic condensation product Which com: prises partially curing the same in a mechanical mold, removing the molding from the said mold and placing it Within a liquid, heating the said liquid, heating the interior of the said molding to a higher temperature than that ot the said liquid and subjecting the liquid tohigh pressure.

The method oit treating moldings ol phenolic condensation product lwhich comprises p rtially curing the saine in a mold, removing the molding from the said mold and submerging it within a body el liquid chemically neutral to the material of the `said molding, heating the said molding both trom the interior and the exterior, the tem perature ol the interior being greater than that of the exterior, and subjecting the said liquid to pressure to cause portions thereof to enter and become impregnated with the outer portions ot the material of the said molding.

Il. The method of treating moldings of phenolic condensation product which comprises partially curing the same in a mechanical mold, removing the moldingtrom the said mold andsubmerging it in a hot liquid which is chemically neutral to the said phenolic condensation product, contining the said liquid Within a static press, heating the molding Jtrom the interior and the exterior and subjecting the said liquid to a pressure on the order of two thousand pounds per square inch.

5. The method ot' treating moldings ol phenolic condensation product which com` prises partially curing the same in a 1nechanical mold, removing the molding in place upon mandrel et said mold from the said mold and subinerging it together with said mandrel within a body ot liquid which is Chemically neutral to the material ot the said molding, maintaining the liquid at a tenmerature ot su'tlicient height to convert the `said material to product C and simultaneously subjecting the same to high pre,- sure to cause a portion thereof to penetrate :into the body oit the said material and to effect the cure thereof.

6. rl'Che method of treating moldings of phenolic condensation product which com prises partially curing the same in a me chanical mold, removing the molding and mandrel from the said mold and submergiug it Within a body of liquid which is .neutral to the material oi the said molding. maintaining the liquid at a temperature olf approximately 1400 rentigra-de and causing 'portions thereol to penetrate into the body oit the said molding.

i'. The method ol treating moldings oit phenolic condensation product which comprises partially curing the same in a mechanical mold, removing the molding from the said mold and submerging it Within a body of molten cumar7 maintaining the latter at a temperature ot approximately 1400 centigrade and causing portions thereof to penetrate into the body of the said mold- 8. The method ot treating moldings oit phenolic condensation product which comprises partially curing the same in a mechanical mold, ren'ioyii'ig the molding :from the said mold and submerging it Within a hot liquid. which is chemically' .neutral to the material ot the molding, simultaneously heating the interior ot the said molding and the said liquid, the temperature of 'the interior uof the said molding being greater than that of the liquid and the said temperature being approximately 140 centigrade and causing portions Oli the said liquid to penetrate and combine with a part of the surface ont the said body of the said molding.

9. 'lhe method of treating moldings of phenolic condensation product which comprises partially curing` the same .in a mechanical mold, removing the molding from the said mold and submerging same Within a body of liquid consisting oi: molten material of a character which is neutral to the material oli the said molding, maintaining the said liquid at a temperature suiiicient to transform product A to product C, heating the interior ot the said molding to a temperature greater than that of the said liquid, subjecting the said liquid to high pressure to cause the said liquid to penetrate into a part of the material oi the said molding and maintaining the interior sui-tace ot the said molding against distortion.

l0. The method ot 'treating moldings of phenolic condensation product which com prises supporting the molding upon a mandrel and submerging the same Within a body ol molten euinar Within a static press, applying' heat to the said molten cumar7 to maintain the same at a temperature ol' ajipro'ximately i400 centigrade, applying heat to the interior of the molding to maintain it at a Atemperature greater than that ot' the temperature ot the exterior oft the molding and subjecting the molten cumar to a pressure on the order ot two thousand pounds per square inch.

ll. rl`he method ot treating moldings oli pheni'ilic condensation j iroduet which con-- sists in submerging the same within a liquid dielectric, maintaining the said liquid at a tenijiierature ot approximately lll-OO centigrade. and simultaneously subjecting the said liquid and the molding therein to high pressure.. the pressure causing a portion ot said dielectric to penetrate said moldingl2. The method of' treating partially cured moldings of phenolic condensation product Which consists in submerging a molding Within a suitable liquid dielectric, supporting the said molding interiorly, maintaining the said liquid and the said molding at a temperature of approximately 140 centigrade and simultaneously subjecting the said liquid to high pressure, and heating the mold interiorly.

13. The method oi treating partially cured moldings of phenolic condensation product which consists in submerging a molding Within a volume of molten cumar, maintaining the said cumar and the said molding at a temperature of approximately 140O centigrade and causing portions of the, cumar77 to penetrate into the body o'll said molding, l

14s. rlhe method of treating partially cured moldings of phenoliccondensation product which consists in submerging a molding Within a volume ol molten Vcccumar, mainn taining the said cumar and the said'molding at a temperature of approximately MOO centigrade and simultaneously subjecting the said molten cumar to a pressure olE the order of twothousand pounds persquare inch.

l5. The method of treating partially cured moldings of phenolic condensation product which vconsists in subinerging a molding Within a volume ot liquid neutral to the said molding, supporting the said molding interiorly, maintaining the said liquid and the said molding at a temperature of approximately la()O centigrade and subjecting the liquid to aL pressure oit the order of two thousand pounds per squarey inch.

1G. The method of treating partially cured phenolic condensation products of heterogeneous density, which consists in subjecting. thev product to the action of a chemically neutral liquid dielectric of greater Viscosity than Water, under pressure on the order of a ton per square inch and ata temperature on the order of 140 C., the pressure causing a portion of said dielectric to penetrate said molding.

17. The method of treating a partially cured phenolic condensation product of heterogenous density, Which consists in subjecting the product to the action o'l' a dielectric material under heat and static pressure, the said material being in a viscous liquidy state during said treatment, and be? coming a solid at normal atmospheric temperature, the pressure causing aportion of said dielectric to penetrate said molding.

18. The method of treating a partially cured phenolic condensation product of heterogeneous density which consists, in subjecting the product to the ten'iperature and pressure actions of a completely polymerizedchemically neutral liquid dielectric, the temperature and pressure of' said liquid being sullicient to transform product A to produce G, to cause a portion ot' said dielectric to pei'ietrate said molding and' to eli'ect an increased' and substantially homogeneous den-l sity of said' product.

19. The method ol treating a partially f cured phenolic condensation product olf' hety erogeneous density which consists in subjecting the product to sulicient temperature, pressure and impregnating actions ol a completely polymer-ized chemically neutral` material for suliicient time to transform product il` to product C to ell'ect an increased and substantially" homogeneous density, and tov superlicially impregnate the exposed surface of said, product, and in slowly cooliifigv said treated product to normal atmospheric temperature, the lsaid material being a liquid during` treatment and becoming a mechanically bonded solid Vin the impregnated por-y tion oil the treated product When cooled to Said normal temperature. l

In testimony that l claim the foregoing as my invention, I have hereunto signed my name this 22nd day ol' July, A. D., 1924.

FRANKLIN s. sMrrH.; i 

